Conventionally, as shown in, e.g., Patent Document 1, an optical sensor has been proposed in which a plurality of photodiodes are formed on a semiconductor substrate, a light transparent layer having a light transparent property is formed on the surface thereof where the photodiodes are formed, a light blocking mask having a light blocking property is formed on the upper surface of the light transparent layer, and a plurality of light propagation areas are formed in the light blocking mask. In the optical sensor, by the light propagation areas of the light blocking mask, the range of light incident on the light receiving surface of each of the photodiodes, especially the elevation angle thereof is defined.
In the optical sensor shown in Patent Document 1, as shown in FIG. 1 of Patent Document 1, the area of the light receiving surface of each of the photodiodes is substantially the same as that of each of the light propagation areas. Accordingly, the angle range (directivity) of the light incident on the light receiving surface of each of the photodiodes is narrow, which may cause the problem that light having a given angle cannot be detected with the photodiode. Therefore, in the case of the structure of the optical sensor described in Patent Document 1, it may be difficult to detect the intensity of light (amount of incident light) or the angles (elevation angle and light-right angle) thereof based on an output signal from each of the photodiodes.
Also, in the optical sensor shown in Patent Document 1, the one-layer light blocking mask is formed on the upper surface of the light transparent layer. In the case of this configuration, light incident from a given one of the light propagation areas may be incident on the photodiode which does not correspond to the given light propagation area via the light transparent layer. As a result, an output signal from the photodiode may include a light output (disturbance output) from the unintended light propagation area.
Also, in the optical sensor shown in Patent Document 1, the two paired photodiodes are adjacent in a right-left direction, and the range of light incident on the light receiving surface of each of the two photodiodes is defined by the one of the light propagation areas located over the two photodiodes. Accordingly, when light is incident on the optical sensor from the left side, an output signal from the right photodiode is larger than an output signal from the left photodiode. Conversely, when light is incident on the optical sensor from the right side, the output signal from the left photodiode is larger than the output signal from the right photodiode. Therefore, by comparing the output signals from the two paired photodiodes with each other, it is possible to detect from which one of the left and right sides light is incident.
In the configuration described above, it is possible to calculate a value (first value) by dividing the output signal from the left photodiode by the total sum of the output signals from the two paired photodiodes, calculate a value (second value) by dividing the output signal from the right photodiode by the total sum of the output signals from the two paired photodiodes, determine a ratio between the two values, and thereby detect how much light is incident on the optical sensor from the left side or from the right side. That is, the right-left ratio of light can be detected.
However, the right-left ratio has a property of varying in accordance with the elevation angle of light and, with only the right-left ratio, a precise incident direction (elevation angle and right-left angle) of light cannot be detected.
Moreover, when there is an angle of light particularly desired to be detected to meet a use purpose, the light propagation areas should be produced again according to the use purpose, which results in the problem of low versatility.
Also, in Patent Document 1, the light blocking mask is formed on the surface (right receiving surface) where the photodiodes are formed via the light transparent layer, and the light propagation areas are formed in the light blocking mask. Light coming obliquely from above and incident on the light receiving surface of each of the photodiodes is blocked by the light blocking mask, but the range in which the light is incident on the surface where the photodiodes are formed depends on the distance between the light receiving surface and the light propagation area. In Patent Document 1, the distance therebetween is determined by the thickness of the light transparent layer and, because the thickness is small, the range of the light incident on the surface where the photodiodes are formed is narrow.
This results in a case where, depending on the incident direction of light, the light is incident on the light receiving surface of the left photodiode, but is not incident on the light receiving surface of the right photodiode. In this case, the output signal from the right photodiode is zero so that the total sum of the output signals from the two photodiodes is equal to the output signal from the left photodiode, the first value is 1, and the second value is 0. Conversely, when the light is incident on the light receiving surface of the right photodiode but is not incident on the light receiving surface of the left photodiode, the output signal from the left photodiode is zero so that the total sum of the output signals from the two photodiodes is equal to the output signal from the right photodiode, the first value is 0, and the second value is 1. Thus, each of the values is constant (saturated) so that, even though it is possible to detect from which one of the left and right sides the light is incident, it is impossible to detect the right-left ratio of the light corresponding to the incident angles of the light.
Also, as shown in, e.g., Patent Document 2, a semiconductor device has conventionally been proposed in which a photosensor and a signal processing circuit are formed in a semiconductor chip. In this semiconductor device, over the photosensor and a signal processing circuit, a first light-transmissive insulating film, a light-transmissive interlayer insulating film, a light blocking film having a window opened therein to expose a light receiving surface, and a light-transmissive chip protecting film are successively stacked in layers, and the other layers stacked on the light receiving surface of the first light-transmissive insulating film are removed to expose the first light-transmissive insulating film. This allows the intensity of light incident on the semiconductor device to be accurately detected even when the intensity of the light is extremely low. In addition, when the light is incident on the multilayer film, the light advances while being reflected and transmitted between the layers before reaching the photosensor so that the light incident on the photosensor undergoes intensity variations due to interference. However, since the other layers stacked on the light receiving surface of the first light-transmissive insulating film have been removed, the light incident on the photosensor is inhibited from including the intensity variations due to interference.
The amount of light (intensity of light) incident on the photosensor depends on the incident angles of the light. However, the semiconductor device shown in Patent Document 2 does not have the function of detecting the incident angles of light. Consequently, the detected light intensity includes intensity variations in accordance with the incident angles of the light so that the accuracy of detection of the light intensity has presented a problem.
Also, as shown in, e.g., Patent Document 3, an optical sensor has conventionally been proposed which includes light receiving elements each for outputting a signal in accordance with the amount of light, and a light-amount changing member supported over the light receiving elements to change the amount of light to each of the light receiving elements in accordance with the incident angles of the light. To each of the light receiving elements, a current-voltage conversion circuit including an operational amplifier and laser trimming resistors is connected. By adjusting the resistance value of each of the laser trimming resistors, the gain of an output signal from each of the light receiving elements is adjusted.
As described above, in the optical sensor shown in Patent Document 3, the current-voltage conversion circuit is connected to each of the light receiving elements, and the resistance values of the laser trimming resistors, the number of which is the same as that of the light receiving elements, are adjusted by laser trimming. Accordingly, the problem of increased cost may occur.
Also, as shown in, e.g., Patent Document 4, an optical sensor has conventionally been proposed which includes a light receiving means in which a plurality of light receiving elements are arranged in the form of a matrix, a defining means for defining the range of radiation of incident light radiated toward the plurality of light receiving elements in accordance with the incident angles of light incident on the light receiving means, and an amplifying means for amplifying a detection signal outputted from each of the plurality of light receiving elements with an amplification factor set based on the position of the light receiving element, and outputting the amplified detection signal. As shown in FIGS. 1 to 3 of Patent Document 4, a cover is provided over the light receiving means, and has a light blocking plate (defining means) having one light passing hole formed in the middle thereof. The optical sensor has a configuration in which the aperture area of the light passing hole is larger than light receiving area of each of the light receiving elements, and light incident on the light receiving means through the light passing hole is incident on the plurality of light receiving elements.
As described above, in the optical sensor shown in Patent Document 4, the one light passing hole corresponds to the plurality of light receiving elements, and the aperture area is larger than the light receiving area. Accordingly, the angle range (directivity) of light incident on the light receiving surface of each of the light receiving elements is wide so that a difference is less likely to occur between the directivity characteristics of the respective light receiving elements. As a result, when the incident angles of light are to be detected based on respective output signals from the plurality of light receiving elements, the accuracy of detection of the incident angles may present a difficulty.